microwave basics

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Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.

Microwave Principle

Hesham Abd El AleemVF IP MW Swap Project


Objectives

Upon completion of this course, you will be able to: Know the technical background of the Microwave and its b

asic concepts Describe Types of Microwave Transmissions systems


Contents

Introduction to Microwave Network Design

Types of Microwave Transmissions.

Microwave Transmission Frequency Bands.

Microwave configurations.

Design Aspects and Main Concepts

Performance and availability objectives


Introduction to Microwave Network Design

The main objective for system planning is to ensure that the radio relay system will meet the given performance and availability requirements.

Quality and availability of communications line-of-sight (LOS) radio are closely related to propagation conditions.


Transmission Types

Two methods of classifications

• Point to point and point to multi point.• Line of sight and non line of sight.


Point to point:

1 transmitter and 1 receiver.

Directive antennas used.

Low radiated power.

Point to multi point:

1 Base station connected to many stations.

Omni directional antenna used for base station.

High radiated power.

Transmission Types : Point to point and point to multi point


Transmission Types

Line of Sight (LOS):

Simple design. Full or partial clearance of fresnel zone. Suitable for long links.


Line-of-Sight Considerations

Microwave radio communication requires a clear line-of-sight (LOS) condition.

Radio LOS takes into account the concept of Fresnel ellipsoids and their clearance criteria.

The Fresnel Zone must be clear of all obstructions.


x

y

d=x+yR

Radius of the first Fresnel zone

R=17.32(x(d-x)/fd)1/2R=17.32(x(d-x)/fd)1/2

where d = distance between antennas (in Km) R= first Fresnel zone radius in meters f= frequency in GHz


Frequency Bands

The following bands are available: Long Haul:

2 , 6 , 7 and 8 GHz Short Haul:

11 , 13 , 15 , 18 , 23 , 25 , 28 and 32 GHz Micro Links:

38 GHz.


Frequency Plans

Lower band Upper band

Channel bandwidth

Channel spacing

According to ITU recommendation for each band.The recommendation specifies the channel bandwidth, spacing and total number of available channels.


Frequency Plans

Frequency channel arrangements The available frequency band is subdivided into two halves, a lower (go) and an upper (return) duplex half. The duplex spacing is always sufficiently large so that the radio equipment can operate interference free under duplex operation. The width of each channel depends on the capacity of the radio link and the type of modulation used

The most important goal of frequency planning is to allocate available channels to the different links in the network without exceeding the quality and availability objectives of the individual links because of radio interference.


LU Uf1 HP f1 VP f1 HP

Frequency planning for MW network

Chain/cascade configuration


Use higher frequency bands for shorter hops and lower frequency bands for longer hopsAvoid lower frequency bands in urban areas.

Use star and hub configurations for smaller networks and ring configuration for larger networks.

In areas with heavy precipitation , if possible, use frequency bands below 10 GHz.

Use protected systems (1+1) for all important and/or high-capacity links.

Leave enough spare capacity for future expansion of the system.

Basic Recommendations


Microwave configurations

1+0 configuration

• One Main Indoor Unit (Main IDU) incorporating the baseband processing and offering tributaries interfaces as well as service channel and supervision. The IDU is frequency independent (same unit from 7/8 up to 38 GHz).• One Outdoor Unit (ODU) incorporating the complete RF transceiver and an integrated or separated antenna. The ODU is capacity independent.• One integrated or non-integrated antenna


1+1 HSB


2x ODUs at same frequency2x antennas single polarization

1+1 HSB SD


1+1 FD

2x ODUs at different frequencies2x antennas single polarization


2x ODUs at different frequencies1 antenna dual polarization


Microwave Link Design is a methodical, systematic and sometimes lengthy process that includes:

Loss/attenuation Calculations

Fading and fade margins calculations

Frequency planning and interference calculations

Quality and availability calculations

Design Aspects and Main Concepts


Performance and availability objectives

Link Availability

A microwave link is available if communication is established in the two directions with an acceptable bit error rate (BER).

If the BER of the communication in at least one direction exceeds the BER specified, the link is considered unavailable.

%Availability=100-%Unavailability.


Error performance parameters are derived from thefollowing events

Errored second (ES):It is a one second period in which one or more bits are in error or

during which loss of signal or alarm indication is detected..

Severely errored second (SES):It is a one second period which has a bit error ratio≥10-3

Parameters are:

Errored second ratio (ESR):the ratio of ES to total seconds in available time during a fixed

measurement interval.

Severely errored second ratio (SESR):the ratio of SES to total seconds in available time during a fixed

measurement interval.


Period of unavailable timebegins at the onset of 10 consecutive SES events. These 10 s are part of unavailable time.

Period of available timebegins at the onset of 10 consecutive non SES events. These 10 s are part of available time.A path is available if, and only if, both directions are available.

Quality (SES) and Availability objectives are chosen according to different ITU recommendations.

Different ITU recommendations depend on the capacities and hop lengths and frequency.

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